Lecithin is well known for its effectiveness as a release agent. Lecithin has provided release capabilities to the products and processes of many different industries, such as the pulp and paper making industry, the various mold making industries, e.g., for paper, plastic, composite material, cement:, clay, textile, rubber and ceramic molding, and the food industry, among others. For a discussion of the many properties and capabilities of Lecithin, see "The Lecithin Book. A Guide to Lecithin.", Central Soya, Chemurgy Division (June 1991), the disclosure of which is incorporated herein by reference.
Lecithin is generally used in combination with a solvent such as, for example, a fatty acid or an oil. The use of lecithin alone as a release agent, or in combination with a solvent, such as a fatty acid or oil, is described, for example, in U.S. Pat. Nos. 5,372,637, 5,034,097 and 5,328,567, the disclosures of which are incorporated herein by reference.
Lecithin alone, or in combination with a fatty acid or an oil, however, is an oil-based mixture. Neither lecithin alone, or an oil-based mixture of lecithin is capable of easily forming a stable aqueous composition. Many of the desired uses of a lecithin-based release aid composition however, are in aqueous-based products or processes which involve contact with water. Thus, a stable aqueous-based release aid composition that is dispersible in water is frequently the industry-needed or desired form of a release aid composition.
The industries that use release aid compositions have long faced the difficulty of having to prepare an aqueous-based emulsion from oil-based release aid compositions. The use of aqueous-based emulsions requires the preparation of the aqueous-based emulsions of the release aid compositions immediately prior to the use of the compositions. The process of preparing such aqueous-based emulsions is a complex process requiring special ingredients and proper blending and emulsifying. Thus, for many industries the process of preparing such emulsions is too complicated or expensive, or is at least seen as a difficult and complex process that is far from the industry's area of speciality.
For example, in the paper making industry, which uses release aids in the majority of their paper making processes and/or products, an aqueous-based release aid emulsion must be formed just prior to use and then immediately used before separation of the emulsion occurs. An additional complication to the process of preparing and using an aqueous emulsion of a release aid composition is that if the emulsion will not be used shortly after preparation, constant agitation is required in order to retain the emulsion and prevent separation of the oil and water emulsion components.
The characteristic separation of oil and water emulsions has complicated many uses of existing release aid compositions. Common uses, such as spraying or coating surfaces with release aid compositions, can be problematic because the emulsion components separate and the spraying or coating processes produce uneven coverage. In addition, due to such separation, it is difficult to achieve the desired dispersion of the emulsion in order to spray the composition onto various surfaces.
The complications regarding the lack of stability of aqueous-based release aid compositions have prevented industries from being able to purchase and store ready-to-use forms of aqueous release aid compositions. The availability of a stable aqueous-based release aid composition is therefore a desired product in many various industries because it would remove the complications and expenses surrounding the preparation of and use of aqueous-based release aid compositions.
Thus, there is an existing need and desire for stable aqueous release aid emulsions capable of providing release capabilities to a wide range of viscous substances and release surfaces.